(1) Field of the Invention
The invention relates to a tool for crushing coke, including                a casing which, in the operational state is connected to a drill rod and on or in which at least one cutting nozzle each for cutting and one drill nozzle for drilling of coke and at least one valve for controlling a direction of flow of the water flowing through the drill rod and the casing through the cutting nozzle and the drill nozzle is arranged.        
(2) Background Art
In oil refineries the last, otherwise no longer usable fraction of the crude oil is converted into coke. The conversion is brought about by feeding this fraction into drums which, as the operation proceeds, become filled with coke. Once the maximum filling level of the drums has been attained, the coke is cut out of the drums.
This so-called “de-coking” is conventionally performed with high pressure water jets which crush the coke and flush it out of the drums. The tool for generating these high pressure water jets is introduced by way of a drill rod mechanism from above into the drum. The “de-coking” is performed in two steps. To begin with, an aperture is drilled by the tool in the drum, then the tool is, once again, taken to the upper end of the drum and the coke is now crushed by high pressure water jets generated by the cutting nozzles approximately at about right angles to the axis.
The tool which is, for example, known from WO 03/14261 A1 representing the genus, is accordingly designed for two operating conditions, firstly for the drilling of an aperture which is necessary for moving the tool and for the subsequent discharge of crushed coke and, secondly, for the cutting of the coke across the cross section of the drum. Accordingly, the drill nozzles direct high pressure water jets essentially parallel or at an acute angle to an axis, which is formed by the drill rod and by the aperture formed during drilling. The cutting nozzles, on the other hand, generate high pressure water jets which are directed essentially at right angles or at a shallow angle to the axis formed by the drilling rod and the aperture in the drum.
The change-over between the operational states of drilling and cutting must proceed rapidly and simply. The nozzles which are used in the tool, due to the high water pressure, suffer wear and tear and must be replaced at regular intervals. Accordingly, the tool must be so designed that a replacement of the nozzles can be performed rapidly and reliably.
The wear and tear of the nozzles is increased by the fact that in known tools of the afore mentioned type, water under high pressure is forced into an annular space which communicates with all nozzles, from where the water enters non-directionally into whichever nozzles are opened, in the course of which no reorientation whatsoever of the flow in the direction of the respective nozzles takes place.
In another tool as well, known from DE 39 41 953 A1 the feeding of water under pressure to the cutting nozzles and to the drill nozzles proceeds initially in a central piston and from there, depending on the position of the piston in the casing of the tool, through apertures traversing the wall of the piston into one or two annular cavities of which one is connected to the cutting nozzles and the other is connected to the drill nozzles. The pressurized water flow is subjected in the piston to vortex formation and, only after having suffered corresponding pressure and flow losses, passes by way of the apertures in the wall of the piston into radial ducts in which the water is conducted to the nozzles.
In the tool known from U.S. Pat. No. 5,816,505 as well, two annular cavities of this type are provided to each of which the pressurized water is conducted, as a function of a control bringing about either the drilling mode of operation or the cutting mode, with considerable flow losses and forwarded from the respective annular cavity by way of ducts connected there to the nozzles.